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Protection for servo motors using Home Work Board-Breadboard — Parallax Forums

Protection for servo motors using Home Work Board-Breadboard

ArchiverArchiver Posts: 46,084
edited 2004-03-19 19:08 in General Discussion
Hi,.

I damaged two servo motors easily,
using the Home Work Board-Breadboard.

When I connected the 6 volts power
supply they burned.
My mistake was that I reversed the polarity
for less than one second
(I know,I know it was my mistake)

The Basic Stamp Home Work Board is working.
(no problem)

The Board of educations have a mechanical protection
but I don't want to buy a board of education.

How can I protect the servo motors for a
reversed polarity?

Diode? or something like that.

Thanks in advance: Joe

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Comments

  • ArchiverArchiver Posts: 46,084
    edited 2004-03-18 16:05
    You could certainly put diodes (like 1N4001) inline with the positive
    side of the supply (keep in mind you'll lose about 0.7v through the
    diode) -- but I wouldn't bother. I've reverse connected servos more
    than once and never killed them. Are you sure it wasn't something else?

    -- Jon Williams
    -- Applications Engineer, Parallax
    -- Dallas Office


    Original Message
    From: Joe Terk [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=vljpu6ICNp5bkYsqSWC4hjSDDUsLGH1BacYmVzm4wXYp8O8lkOMHpwQZSSC7ExmzBodt2ABJi78ro3tF]joeterk@y...[/url
    Sent: Thursday, March 18, 2004 9:00 AM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] Protection for servo motors using Home Work
    Board-Breadboard


    Hi,.

    I damaged two servo motors easily,
    using the Home Work Board-Breadboard.

    When I connected the 6 volts power
    supply they burned.
    My mistake was that I reversed the polarity
    for less than one second
    (I know,I know it was my mistake)

    The Basic Stamp Home Work Board is working.
    (no problem)

    The Board of educations have a mechanical protection
    but I don't want to buy a board of education.

    How can I protect the servo motors for a
    reversed polarity?

    Diode? or something like that.

    Thanks in advance: Joe

    __________________________________
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  • ArchiverArchiver Posts: 46,084
    edited 2004-03-18 16:11
    Hello Joe.



    > I damaged two servo motors easily,

    > using the Home Work Board-Breadboard.

    >

    > When I connected the 6 volts power

    > supply they burned.

    > My mistake was that I reversed the polarity

    > for less than one second

    > (I know,I know it was my mistake)



    With the BOE you don't have this problem because you connect the servos to
    the servo port, making it almost impossible to make a bad connection (I said
    almost because you can still reverse connect the servo, but this won't
    destroy it).



    With the HomeWork Board you have to make your own wiring, leaving the door
    open to reverse polarity and other wiring mistakes.



    The circuit inside the servos is using polarized capacitors.

    You cannot provide effective external protection to avoid reversed polarity
    connection to the servo.

    The diode should be added inside the servo case to avoid destroying the
    capacitors.



    As you noticed, capacitors get destroyed almost instantly when reversing
    polarity.



    The only solution is double and triple checking your wiring before applying
    power to the board.



    Saludos,

    Aristides Alvarez

    International Education Program Developer

    aalvarez@p...

    Parallax, Inc. www.parallax.com

    USA
  • ArchiverArchiver Posts: 46,084
    edited 2004-03-18 16:28
    Why yes, a diode in the +5 line would protect
    from reverse voltage -- and it would also drop
    the voltage going to the Servo by 0.6 Volts.
    This could be useful, depending on if you need
    it or not.

    --- In basicstamps@yahoogroups.com, Joe Terk <joeterk@y...> wrote:
    > Hi,.
    >
    > I damaged two servo motors easily,
    > using the Home Work Board-Breadboard.
    >
    > When I connected the 6 volts power
    > supply they burned.
    > My mistake was that I reversed the polarity
    > for less than one second
    > (I know,I know it was my mistake)
    >
    > The Basic Stamp Home Work Board is working.
    > (no problem)
    >
    > The Board of educations have a mechanical protection
    > but I don't want to buy a board of education.
    >
    > How can I protect the servo motors for a
    > reversed polarity?
    >
    > Diode? or something like that.
    >
    > Thanks in advance: Joe
    >
    > __________________________________
    > Do you Yahoo!?
    > Yahoo! Mail - More reliable, more storage, less spam
    > http://mail.yahoo.com
  • ArchiverArchiver Posts: 46,084
    edited 2004-03-19 19:08
    Thanks Allan:

    I tried but the servo worked erratic.
    ( a diode has resistence and the HomeWork
    Stamps have a 220 extra resistor, I don't
    know if the problem is there)

    Thanks
    --- Allan Lane <allan.lane@h...> wrote:
    > Why yes, a diode in the +5 line would protect
    > from reverse voltage -- and it would also drop
    > the voltage going to the Servo by 0.6 Volts.
    > This could be useful, depending on if you need
    > it or not.
    >
    > --- In basicstamps@yahoogroups.com, Joe Terk
    > <joeterk@y...> wrote:
    > > Hi,.
    > >
    > > I damaged two servo motors easily,
    > > using the Home Work Board-Breadboard.
    > >
    > > When I connected the 6 volts power
    > > supply they burned.
    > > My mistake was that I reversed the polarity
    > > for less than one second
    > > (I know,I know it was my mistake)
    > >
    > > The Basic Stamp Home Work Board is working.
    > > (no problem)
    > >
    > > The Board of educations have a mechanical
    > protection
    > > but I don't want to buy a board of education.
    > >
    > > How can I protect the servo motors for a
    > > reversed polarity?
    > >
    > > Diode? or something like that.
    > >
    > > Thanks in advance: Joe
    > >
    > > __________________________________
    > > Do you Yahoo!?
    > > Yahoo! Mail - More reliable, more storage, less
    > spam
    > > http://mail.yahoo.com
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed.
    > Text in the Subject and Body of the message will be
    > ignored.
    >
    > Yahoo! Groups Links
    >
    >
    > basicstamps-unsubscribe@yahoogroups.com
    >
    >
    >


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